Engineered soils are geo-materials designed to address intricate practical problems in geotechnical and geo-environmental applications. One of the key issues for geo-engineers has been to improve soil properties to mitigate indiscriminate geo-hazards, such as contaminant migration in subsurface. The common approaches include physical modification of soil minerals, chemical treatments of soil solids and pore fluids, introduction of anomalous materials, and mixing of several granular materials to achieve desired functionalities.
Advances in material science and surface chemistry permit modifying the surfaces controlled by chemical composition and conformational structure of surface coating. For instance, the surface modification with organosilanes, polymers and carbon nanotube dramatically increases hydrophobicity. Granular materials and membranes coated with functional polymers and organo-silanes can be used for separating immiscible fluids, removing oil from the surface, and sieving hazardous compounds. These approaches render permanent or stationary changes to soil properties, which are often irreversible, hence may be limited in a dynamic environment.
Further, land operations in the petroleum industry cause oil pollution by drilling, leakage from wellheads and pipelines, and overflow at gathering stations. The chemical methods that use dispersants, sorbents or solidifiers for cleanup still introduce toxic materials into the environment. Bioremediation can degrade residual hydrocarbon in secondary phase after the first cleanup, yet it can take a long time with changing nutrient and oxygen supplies. Thermal treatment is only effective to volatile compounds and complete sediment removal is often required for heavily contaminated soil. There are major challenges that remain in our capabilities to govern the fate and migration of spilled oils and oily wastes in subsurface, one of which is efficient fluid separation. Other separation methods include air sparging of non-aqueous phase liquids in contaminated soils and groundwater; liquid water transport in a gas diffusion layer (GDL) in fuel cell applications, and methane hydrate dissociation in deep marine formations. These active separation processes are costly and there are no known methods that have been demonstrated to provide sustainable treatment.
Embodiments of the present invention are directed, inter alia, to solving some of the challenges associated with existing bioremediation processes.